Investigation of thickness and welding residual stress effects on fatigue crack growth

This paper presents a numerical investigation of the effects of thickness and welding residual stress (WRS) on fatigue crack growth (FCG) for centrally cracked steel specimens. Various thicknesses and different welding heat inputs were used to study their influence on WRS distribution, crack driving force, and fatigue life. The effect of mean stress (sigma m) on the crack driving force and crack growth was also discussed. The results showed that thickness significantly influences the crack driving force and fatigue life when WRS is considered. A large crack driving force was obtained at and near the welded surface compared to that generated at the back surface, forming a variable distribution along the crack tip with increasing thickness. FCG rate at the welded surface will be faster than that at the back surface for the thicker specimens. The longest fatigue life with remarkable retardation was obtained under the smallest sigma m when WRS is dominant. The retardation effect disappeared with increasing sigma m. The mechanism controlling crack growth behavior due to the change in sigma m and thickness was also discussed.